1. Field of the Invention
This invention relates to a rotary plug valve and, more particularly, to such a valve which may be locked in a predetermined position. Valves of the class here contemplated find application in gas service lines, for example, to enable gas service to be shut off by locking the valve in its closed position.
2. Description of the Prior Art
It is known from U.S. Pat. No. 3,554,218 to provide a rotary plug valve with a body member having a passage for the flow of fluid therethrough which passage is intersected by a plug seat and a ported valve plug member rotatable in the plug seat between open and closed positions and having an end portion terminating flush with or below the exterior of the valve body member. The end portion of the valve plug member is provided with an axially extending, non-circular socket for receiving an operating head handle member having a non-circular end portion complementary with the socket. The valve body is also provided with a skirt-like extension which surrounds the open end of the plug seat as well as the end portion of the plug member. Suitable bores are provided in the plug member and in the skirt-like extension and these are arranged to be aligned in a selected position of the plug member, preferably the closed position, and into which an elongated plunger-type lock member may be inserted and locked, the handle member having been previously removed. A closure plug is adapted to fit into the socket in the end portion of the valve plug member to protect the end portion of the valve plug member when the valve is locked, the closure member having a bore therethrough arranged to be aligned with the bores in the skirt-like extension of the valve body member and the end portion of the valve plug member so that the closure plug is retained in position by the lock member.
More specifically, and as seen in FIG. 2 of U.S. Pat. No. 3,554,218, the bore in the skirt-like extension of the valve body passes through diametrically opposed portions of the extension as at 40, 40, the bore 44 in the plug member passes through diametrically opposed portions of the plug member defining the socket, the bore in one of the opposed portions of the plug member being of a diameter equal to that of the bore in the skirt-like portion of the valve body while the bore in the other opposed portion of the plug member is of a reduced diameter, as at 45. The bore in the closure plug is actually constituted by a bore 64 and a counterbore 66, the bore 64 being of a diameter equal to that of the bore in the valve body and the counterbore being equal to the bore 45 of reduced diameter in the skirt-like extension.
A conventional elongated locking device 46 is used to secure a valve as described above in closed position. The locking device 46 has an enlarged head 48 and a shank 50 of reduced diameter, the shank carrying a pair of steel balls 52 held in an outwardly extended position by an unshown mechanism in the device 46. A second enlarged head 54 is cup-shaped to receive the shank 50 and has an inner annular groove 56 to receive the balls 52 when the mechanism in the device prevents the balls from moving radially inwardly thus locking the two elements of the device 46 together until a special key is inserted axially through one of the heads to move the mechanism in the device to allow the balls to retract from the groove 56.
It is noted that a portion of the bore 44 is reduced so that the heads of the locking device prevent the device from moving axially when in locked position.
According to this construction then, a skirt-like extension on the body member is used to provide an interface between the valve plug and a removable handle 36 for operating the valve, and between the valve plug and a closure plug 38 that replaces the handle when the valve is to be locked. Thus, a multiplicity of parts are required and since all of the parts are not used at the same time, those not in use are subject to loss and of course extra parts add to overall cost. Moreover, the need to exchange parts when unlocking the valve and to reverse exchange parts when relocking it is cumbersome.
Additionally, since it is desired that no part of the locking device extend beyond the perimeter of the valve body, it is possible to insert the locking device into the valve of U.S. Pat. No. 3,554,218 in one direction only thus rendering its application inconvenient and requiring the entry side of the valve to be clear of adjacent structures. Further, various configurations of the prior device require it to be machined for sufficiently precise fit and this is costly.
It should also be noted that a gas company using these prior art valves would have to equip their personnel with the special handle required to operate the valve; fire and police department personnel would also need such handles to be able to control gas flow in an emergency; plumbers required to do routine maintenance on gas appliances would need the handles; and each customer in certain states are required by law to have a tool on hand to shut off gas in case of earthquake.
It is also known from U.S. Pat. No. 3,560,130 to provide locking means on a valve member and a valve body adapted to prevent movement of the valve member when the same is in a selected position relative to the valve body. To this end, a bore is formed through the valve member perpendicular to its axis while a bore is formed to extend through the valve body at opposite diametral points and in axial alignment with the valve member bore when in a selected position. One end of the bore in the valve body is blind so that a known locking pin such as a pin of the Smith-Morse type having an enlarged head at one end and a reduced shank extending therefrom can be inserted through the aligned bores to lock the valve body and valve member against relative rotation from a selected position. The open bore portion in the valve body receives the head of the locking pin, being of a diameter to accomodate the head, the blind bore and bore in the valve member being of smaller diameter to receive only the locking pin shank.
The locking pin has projecting balls similar in function to those of the locking device previously described, but in this case the balls engage in an annular groove in a cap fixed in the blind portion of the valve body bore, in which case the blind part of the bore is of a larger diameter to accomodate the cap, or the balls may engage in an annular groove in the bore that extends through the valve member.
In the arrangement shown in the embodiments of U.S. Pat. No. 3,560,130 wherein the balls of the locking pin engage in an annular groove in the bore extending through the valve member, the valve member and the valve body must be aligned in one angular position only in order properly to lock the device i.e., a position wherein the balls enter the annular groove when the lock pin head has fully entered the open bore in the valve body. If the bores are aligned with the valve member 180.degree. away from that position, the balls will enter the groove to lock the valve while the locking pin head projects from the body and could readily be attacked.
Additionally, in respect of the prior construction, a certain amount of machining is required to form the blind bore for the cap, if one is used, or to receive the shank of the locking pin. Based upon the size of the valve, other areas of those elements relating to the locking feature may also have to be machined.
It is also noted that the device disclosed in U.S. Pat. No. 3,560,130 is specifically designed to accept only a locking pin of the Smith-Morse type.